diff options
Diffstat (limited to 'arch/arm/mach-sunxi/rmr_switch.S')
| -rw-r--r-- | arch/arm/mach-sunxi/rmr_switch.S | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/arch/arm/mach-sunxi/rmr_switch.S b/arch/arm/mach-sunxi/rmr_switch.S new file mode 100644 index 0000000000..cefa93001b --- /dev/null +++ b/arch/arm/mach-sunxi/rmr_switch.S @@ -0,0 +1,41 @@ +@ +@ ARMv8 RMR reset sequence on Allwinner SoCs. +@ +@ All 64-bit capable Allwinner SoCs reset in AArch32 (and continue to +@ exectute the Boot ROM in this state), so we need to switch to AArch64 +@ at some point. +@ Section G6.2.133 of the ARMv8 ARM describes the Reset Management Register +@ (RMR), which triggers a warm-reset of a core and can request to switch +@ into a different execution state (AArch32 or AArch64). +@ The address at which execution starts after the reset is held in the +@ RVBAR system register, which is architecturally read-only. +@ Allwinner provides a writable alias of this register in MMIO space, so +@ we can easily set the start address of AArch64 code. +@ This code below switches to AArch64 and starts execution at the specified +@ start address. It needs to be assembled by an ARM(32) assembler and +@ the machine code must be inserted as verbatim .word statements into the +@ beginning of the AArch64 U-Boot code. +@ To get the encoded bytes, use: +@ ${CROSS_COMPILE}gcc -c -o rmr_switch.o rmr_switch.S +@ ${CROSS_COMPILE}objdump -d rmr_switch.o +@ +@ The resulting words should be inserted into the U-Boot file at +@ arch/arm/include/asm/arch-sunxi/boot0.h. +@ +@ This file is not build by the U-Boot build system, but provided only as a +@ reference and to be able to regenerate a (probably fixed) version of this +@ code found in encoded form in boot0.h. + +.text + + ldr r1, =0x017000a0 @ MMIO mapped RVBAR[0] register + ldr r0, =0x57aA7add @ start address, to be replaced + str r0, [r1] + dsb sy + isb sy + mrc 15, 0, r0, cr12, cr0, 2 @ read RMR register + orr r0, r0, #3 @ request reset in AArch64 + mcr 15, 0, r0, cr12, cr0, 2 @ write RMR register + isb sy +1: wfi + b 1b |